1. Field of the Invention
The present invention is directed to magnetic position sensors, such as linear position sensors, and more particularly to such sensors having a plurality of magnets configured to generate a signal that varies with a position of the magnets.
2. Description of Related Art
Contactless position sensors are widely known in the art. One kind of contactless sensor uses a magnet attached to a component whose position is to be measured, with a magnetic field sensor at a fixed location, or vice versa, to detect the magnetic field produced by the attached magnet. The sensor measures the magnetic field strength at the location of the sensor, and the detected field strength is used to calculate the location of the magnet. However, the location is not a linear function of the measured field strength, so that the calculation is complicated.
To overcome that difficulty, some position sensors use more than two magnets, a complex shape, or one or two larger magnets, as large as half the range of the distance to be measured, in order to modify the magnetic flux lines to obtain a linear response with the distance. For example, U.S. Pat. No. 7,088,095 uses one or two magnets of complex shapes, and a Hall sensor measures the orthogonal component of the field. The magnets' dimension is as large as the distance range to be measured.
U.S. Pat. No. 7,268,536 uses two magnets arranged such to produce uniform field in the detection region, and a magnetoelectric transducer provides the position measurement. The dimension of the two magnets is as large as half the distance range to be measured. Other prior art devices require flux directors to modify the magnetic field or flux lines from the magnets to obtain as close to a linear output as possible.
What is needed, therefore, is an instrument, system, and method for measuring the distance an object traverses that addresses the deficiencies in the prior art magnetic devices, one that is relatively compact, easy to manufacture, and outputs a substantially linear signal, and does not require flux directors, and also can operate in various high temperature, high humidity, and high vibration environments.